a fluid (gas or liquid) used to cool a device by transferring heat away from one part to another.

Fluid cooling agent.( 099)

A substance circulated through a nuclear reactor to remove or transfer heat. The most common coolants are water and heavy water.

The liquid or gas used to transfer the heat of nuclear fission to a heat-exchanger in which steam is raised for the electrical turbine-generator. The cool liquid or gas is then returned to the reactor. The coolant for the PWR is highly purified water.